Studies have shown that the feeding of antigen orally activates T lymphocytes which can suppress ongoing or induced immunity to the same or closely related antigens. Based upon these findings, it is hypothesized that feeding thyroid stimulating hormone (TSH) receptor, thyroglobulin, or thyroid peroxidase orally might down-modulate the immune reactivity present in Graves' disease or Hashimoto's thyroiditis. In order to test this, a model of Graves' Disease will be developed in mice and the induction of tolerance by oral administration of thyroid stimulating hormone receptor (TSH-R) will be studied. While tolerization to antigen in mice may be quite different from a naturally occurring human response, studies in this model system should provide information on the specificity of tolerance induction, the duration of the tolerant state, the mechanism of the response, and possibly the role of specific T cell epitopes. Ultimately this should help in planning a strategy for use in patients with autoimmune thyroid disease, a disease which causes about 6% of women and 0.6% of men to seek medical attention during their lifetime.